The present invention relates to microwave processing equipment for amplifying or attenuating microwaves and more particularly to microwave processing equipment being suitable to amplify weak electromagnetic waves in the microwave range.
In the prior art, in order to amplify electromagnetic wave in the microwave range, an electron tubes such as a klystron or a traveling wave tube, and semiconductor elements such as a Gunn diode or an impact avalanche and transit time diode, have been used. These electron tubes and semiconductor elements are explained, for example, in Eitaro Abe, "Microwave Technology" (published by Tokyo University shuppankai, Tokyo, 1979) at pp. 127-135.
Among the above-mentioned devices, the electron tubes are applicable to microwave amplifications for broad frequency ranges, but there are problems in that they are large in size and weak to impact force, and high voltage and cooling water must be supplied. Moreover, and their life is short and their performance varies with the passage of time. On the other hand, the semiconductor elements have superior characteristics in handling due to their small size and their ability to operate at lower voltages in comparison to the electron tubes, but have difficulties in their limited frequency range, high price and lack of reliability at present, because the history of development of the semiconductor elements is short in comparison to that of the electron tubes.
Further, in any of these electron tubes and semiconductor elements, since a massive flow of electrons is controlled and amplification is carried out, there is an elementary problem where the flow is accompanied by the generation of noise. This problem becomes particularly serious when microwaves to be amplified are very weak.